At present, a digital processing unit in a wireless transmission device mainly includes a baseband unit and an analog-to-digital (A/D)/digital-to-analog (D/A) conversion device. During data communication between a transmitter and a receiver, data is transmitted in the form of a digital signal or an analog signal. Therefore, conversion between digital signals and analog signals needs to be performed. Using a base station as a transmitter and a wireless terminal as a receiver for example, signal processing implemented by the digital processing unit is as follows: The baseband unit of the base station processes the digital signals, and the digital-to-analog conversion device converts the processed digital signals into analog signals and sends the analog signals to the wireless terminal.
Processing the digital signals by the baseband unit mainly refers to data coding and modulation. A baseband unit includes a Central Processing Unit (CPU), a channel coder, a digital signal processor, a modulator/demodulator, and an interface module. A data coding and modulation process is as follows: First, the CPU controls the interface module to receive digital signals; the channel coder codes the data to obtain coded data in a specific coding format; then the digital signal processor obtains the coded data from the channel coder, and controls the modulator/demodulator to perform data modulation on the coded data according to different modulation manners. The radio service traffic to be processed increases exponentially. Therefore, the percentage of the power consumption of the digital processing unit in the total power consumption of the entire base station gradually increases. It is estimated that in a long term evolution-advanced (LTE-A) system, the power consumption of the digital processing unit will account for more than 30% of the total power consumption of the entire base station. Therefore, how to reduce the power consumption of the digital processing unit will become an important subject for improving energy efficiency of the base station.
As shown in FIG. 1, a flowchart of a method for coding and modulating data in fixed bitwidth manner in the prior art is illustrated. The method for coding and modulating data using the fixed bitwidth includes the following steps:
Step 001: For a wireless terminal, the digital signal processor of the baseband obtains M-bit data sent by the wireless terminal from the channel coder.
In this step, the data bitwidth output once by the channel coder is determined by a coding rate, and the data bitwidth output once by the channel coder is represented by the number of bits; and the data volume required for the digital processing unit to perform modulation once is also represented by the number of bits, where M is a common multiple of the data bitwidth output once by the channel coder and the data volume required for the digital processing unit to perform modulation once.
Step 002: The digital signal processor judges, according to the data modulation manner of the wireless terminal, whether the data modulation manner of the wireless terminal is one of the modulation manners supported by the digital processing unit of the base station. If the data modulation manner of the wireless terminal is one of the modulation modes supported by the digital processing unit of the base station, step 004 is performed; otherwise, step 003 is performed and the data is discarded.
In this step, the data modulation manner of the wireless terminal may be obtained from the wireless terminal, or from packet information carried in the M-bit data.
Step 004: Calculate parameters a and b.
In this step, a is the number of bits required for performing modulation once according to the data modulation manner of the wireless terminal; after a is obtained according to the data modulation manner of the wireless terminal, parameter b is calculated as: b=M/a.
Step 005: Evenly split the M-bit data read in step 001 into b parts, and perform data modulation respectively on each part of data.
In this step, the modulation order corresponding to each modulation bitwidth is preset in the base station, and the digital processing unit codes and modulates each part of data according to a modulation bitwidth a, the corresponding modulation order and coding rate corresponding to a modulation bitwidth a.
For a wireless transmission device where the wireless terminal is used as the receiver and the base station is used as the transmitter, the prior art cannot better solve the problem of low utilization of the digital processing unit with respect to how to properly use the digital processing unit. This is because, during data coding and modulation, the digital processing unit can only determine a fixed bitwidth according to the data modulation manner of the wireless terminal, and the digital processing unit is controlled, according to the modulation order and coding rate corresponding to the fixed bitwidth, to code and modulate the data. However, wireless terminals not having a high requirement for signal quality only need to receive signals modulated using a small bitwidth and low modulation order, which is sent by the base station, to meet their communication requirements. For the base station, low-order modulation using a small bitwidth facilitates reduction of the power consumption of the transmitter. In addition, the precision of the supported bitwidth of the wireless terminal may be far smaller than the fixed bitwidth of the base station. Therefore, when the base station, as the transmitter, codes and modulates, according to the fixed bitwidth, modulation order, and coding rate, the data sent to the wireless terminal, the signal quality of the wireless terminal is not improved and power consumption of the base station is increased, resulting in overdesign of the bitwidth of the existing digital processing unit.